The affiliate, Toyota Industries, did not conduct proper horsepower output testing for the certification of three diesel engine models, the parent group said.
The automaker said the models, including the Land Cruiser 300 and HiAce, use the affected engines.
Toyota Industries said in a separate statement that its workers adjusted the fuel injection amounts to make the data “better-looking”.
Toyota Motor said it had since confirmed that the affected engines and vehicles meet engine performance output standards, meaning there was no need to stop using the affected engines or vehicles.
Toyota Industries also said other irregularities were found in connection with the certification process for engines for forklifts and other construction equipment. The news comes after Toyota subsidiary Daihatsu, which produces popular small vehicles in Japan, had to suspend all shipments last month after it discovered it did not properly conduct vehicle safety tests for decades.
